Gait analysis in rats with peripheral nerve injury

Sticky and Strain-Gradient Artificial Epineurium for Sutureless Nerve Repair in Rodents and Nonhuman Primates

The need for the development of soft materials capable of stably adhering to nerve tissues without any suturing followed by additional damages is at the fore at a time when success in postoperative recovery depends largely on the surgical experience and/or specialized microsuturing skills of the surgeon. Despite fully recognizing such prerequisite conditions, designing the materials with robust adhesion to wet nerves as well as acute/chronic anti-inflammation remains to be resolved. Herein, a sticky and strain-gradient artificial epineurium (SSGAE) that overcomes the most critically challenging aspect for realizing sutureless repair of severely injured nerves is presented. In this regard, the SSGAE with a skin-inspired hierarchical structure entailing strain-gradient layers, anisotropic Janus layers including hydrophobic top and hydrophilic bottom surfaces, and synergistic self-healing capabilities enables immediate and stable neurorrhaphy in both rodent and nonhuman primate models, indicating that the bioinspired materials strategy significantly contributes to translational medicine for effective peripheral nerve repair.

A Preliminary Study on Grip-Induced Nerve Damage Caused by a Soft Pneumatic Elastomeric Gripper

Forceps, clamps, and haemostats are essential surgical tools required for all surgical interventions. While they are widely used to grasp, hold, and manipulate soft tissue, their metallic rigid structure may cause tissue damage due to the potential risk of applying excessive gripping forces. Soft pneumatic surgical grippers fabricated by silicone elastomeric materials with low Young’s modulus may offer a promising solution to minimize this unintentional damage due to their inherent excellent compliance and compressibility. The goal of this work is to evaluate and compare the grip-induced nerve damage caused by the soft pneumatic elastomeric gripper and conventional haemostats during surgical manipulation. Twenty-four Wistar rats (male, seven weeks) are subjected to sciatic nerve compression (right hind limb) using the soft pneumatic elastomer gripper and haemostats. A histopathological analysis is conducted at different time-points (Day 0, Day 3, Day 7 and Day 13) after the nerve compression to examine the morphological tissue changes between the rats in the ‘soft gripper’ group and the ‘haemostats’ group. A free walking analysis is also performed to examine the walking function of the rats after recovery from different time points. Comparing the rigid haemostats and soft gripper groups, there is a visible difference in the degree of axonal vacuolar degeneration between the groups, which could suggest the presence of substantial nerve damage in the ‘haemostats’ group. The rats in the haemostats group exhibited reduced right hind paw pressure and paw size after the nerve compression. It shows that the rats tend not to exert more force on the affected right hind limb in the haemostats group compared to the soft gripper group. In addition, the stance duration was reduced in the injured right hind limb compared to the normal left hind limb in the haemostats group. These observations show that the soft pneumatic surgical gripper made of silicone elastomeric materials might reduce the severity of grip-induced damage by providing a safe compliant grip compared to the conventional haemostats. The soft pneumatic elastomer gripper could complement the current surgical gripping tool in delicate tissue manipulation.

Functional Reconstruction of Denervated Muscle by Xenotransplantation of Neural Cells from Porcine to Rat

Neural cell transplantation targeting peripheral nerves is a potential treatment regime for denervated muscle atrophy. This study aimed to develop a new therapeutic technique for intractable muscle atrophy by the xenotransplantation of neural stem cells derived from pig fetuses into peripheral nerves. In this study, we created a denervation model using neurotomy in nude rats and transplanted pig-fetus-derived neural stem cells into the cut nerve stump. Three months after transplantation, the survival of neural cells, the number and area of regenerated axons, and the degree of functional recovery by electrical stimulation of peripheral nerves were compared among the gestational ages (E 22, E 27, E 45) of the pigs. Transplanted neural cells were engrafted at all ages. Functional recovery by electric stimulation was observed at age E 22 and E 27. This study shows that the xenotransplantation of fetal porcine neural stem cells can restore denervated muscle function. When combined with medical engineering, this technology can help in developing a new therapy for paralysis.

A Therapeutic Strategy for Lower Motor Neuron Disease and Injury Integrating Neural Stem Cell Transplantation and Functional Electrical Stimulation in a Rat Model

Promising treatments for upper motor neuron disease are emerging in which motor function is restored by brain–computer interfaces and functional electrical stimulation. At present, such technologies and procedures are not applicable to lower motor neuron disease. We propose a novel therapeutic strategy for lower motor neuron disease and injury integrating neural stem cell transplantation with our new functional electrical stimulation control system. In a rat sciatic nerve transection model, we transplanted embryonic spinal neural stem cells into the distal stump of the peripheral nerve to reinnervate denervated muscle, and subsequently demonstrated that highly responsive limb movement similar to that of a healthy limb could be attained with a wirelessly powered two-channel neurostimulator that we developed. This unique technology, which can reinnervate and precisely move previously denervated muscles that were unresponsive to electrical stimulation, contributes to improving the condition of patients suffering from intractable diseases of paralysis and traumatic injury.

Peripheral Nerve Regeneration with Acellular Nerve Allografts Seeded with Amniotic Fluid-Derived Stem Cells

Introduction

Tissue engineering strategies have attempted to mimic regenerating axons' environment by adding supportive types of cells other than Schwann cell to the nerve allograft. We hypothesized that allografts can be seeded with amniotic fluid-derived stem cells (AFS) to promote nerve regeneration.

Methods

ANAs with AFS cells for long-gap nerve repairs were studied using a rat model. A sciatic nerve injury was created and repaired immediately with a rat acellular nerve allograft (ANA) construct alone, an ANA construct seeded with AFS cells, or with an autograft. Walking track analysis and electrophysiology were performed to document the return of motor control at 4 months post injury. Axon morphology on the nerve segments was assessed.

Results

In vivo gait analysis showed that the ANA plus AFS cell group had significantly advanced recoveries in overlap distance, paw angle degree, paw drag, stance width, axis distance, and sciatic function index (SFI) compared with ANA alone. The ANA plus AFS cell group also demonstrated greater gastrocnemius compound muscle action potential (CMAP) ratio, sciatic axon diameter, fiber diameter, myelin thickness, G ratio (average axonal diameter (AD)/fiber diameter (FD)), and neuromuscular junction (NMJ) numbers compared to ANA. Discussion. The allograft plus AFS cell group demonstrated significantly improved functional and histological outcomes compared to allograft group alone, showing no significant difference of the nerve regeneration from the autograft group. Thus, AFS cells may be a suitable cell source to replace Schwann cells to support and accelerate peripheral nerve regeneration following large-gap nerve injury.

Nanogels with High Loading of Anesthetic Nanocrystals for Extended Duration of Sciatic Nerve Block

The development of thermoresponsive nanogels loaded with nanocrystals of the local anesthetic bupivacaine nanocrystals (BNCs) for prolonged peripheral nerve pain relief is reported here. BNCs were prepared using the antisolvent precipitation method from the hydrophobic form of bupivacaine (bupivacaine free base). The as-prepared BNCs were used stand-alone or encapsulated in temperature-responsive poly(ethylene glycol) methyl ether methacrylate (OEGMA)-based nanogels, resulting in bupivacaine NC-loaded nanogels (BNC-nanogels) of monodisperse size. The synthesis protocol has rendered high drug loadings (i.e., 93.8 ± 1.5 and 84.8 ± 1.2 wt % for the NC and BNC-nanogels, respectively) and fast drug dissolution kinetics in the resulting composite material. In vivo tests demonstrated the efficacy of the formulation along with an extended duration of sciatic nerve block in murine models of more than 8 h with a formulation containing only 2 mg of the local anesthetic thanks to the thermoresponsive character of the polymer, which, at body temperature, becomes hydrophobic and acts as a diffusion barrier for the encapsulated drug nanocrystals. The hydrophobicity of the encapsulated bupivacaine free base probably facilitates its pass through cell membranes and also binds strongly to their hydrophobic lipid bilayer, thereby protecting molecules from diffusion to extracellular media and to the bloodstream, reducing their clearance. When using BNC-nanogels, the duration of the anesthetic blockage lasted twice as long as compared to the effect of just BNCs or a conventional bupivacaine hydrochloride solution both containing equivalent amounts of the free drug. Results of the in vivo tests showed enough sensory nerve block to potentially relieve pain, but still having mobility in the limb, which enables motor function when required. The BNC-nanogels presented minimal toxicity in the in vivo study due to their sustained drug release and excellent biocompatibility. The encapsulation of nano-sized crystals of bupivacaine provides a prolonged regional anesthesia with reduced toxicity, which could be advantageous in the management of chronic pain.

Astrocyte reactivity in spinal cord and functional impairment after tendon injury in rats

Astrocyte reactivity in the spinal cord may occur after peripheral neural damage. However, there is no data to report such reactivity after Achilles tendon injury. We investigate whether changes occur in the spinal cord, mechanical sensitivity and gait in two phases of repair after Achilles tendon injury. Wistar rats were divided into groups: control (CTRL, without rupture), 2 days post-injury (RUP2) and 21 days post-injury (RUP21). Functional and mechanical sensitivity tests were performed at 2 and 21 days post-injury (dpi). The spinal cords were processed, cryosectioned and activated astrocytes were immunostained by GFAP at 21 dpi. Astrocyte reactivity was observed in the L5 segment of the spinal cord with predominance in the white matter regions and decrease in the mechanical threshold of the ipsilateral paw only in RUP2. However, there was gait impairment in both RUP2 and RUP21. We conclude that during the acute phase of Achilles tendon repairment, there was astrocyte reactivity in the spinal cord and impairment of mechanical sensitivity and gait, whereas in the chronic phase only gait remains compromised.

RNU (Foxn1 RNU-Nude) Rats Demonstrate an Improved Ability to Regenerate Muscle in a Volumetric Muscle Injury Compared to Sprague Dawley Rats

Products developed for skeletal muscle regeneration frequently incorporate allogeneic and xenogeneic materials to elicit a regenerative response to heal skeletal muscle wounds. To avoid graft rejection in preclinical studies, immunodeficient rodents are used. Whether the immunodeficiency alters the host response to the material in skeletal muscle has not been studied. In this study, we hypothesized that an allogeneic acellular skeletal muscle grafts implanted in an immunodeficient rat (RNU, Foxn1-deficient) would exhibit better new muscle fiber formation compared to grafts implanted in immunocompetent Sprague Dawley (SD) rats. Decellularized SD skeletal muscle matrix (DMM) was implanted in the gastrocnemius (N = 8 rats/group). 56 days after surgery, animal gait was examined and animals were euthanized. Muscle force was assessed and fiber number as well as immune cell infiltrate was measured by histomorphometry and immunohistochemistry. Animal gait and percent recovery of muscle force were unchanged in both groups, but newly regenerated muscle fibers increased in RNU rats. Macrophage staining for CD68 was higher in RNU rats than in SD rats. These data show differences in muscle regeneration between animal models using the same biomaterial treatment, but these differences could not be ascribed to the immune response. Overall, our data provide awareness that more studies are needed to understand how host responses to biomaterials differ based on the animal model used.

Combined Use of Chitosan and Olfactory Mucosa Mesenchymal Stem/Stromal Cells to Promote Peripheral Nerve Regeneration In Vivo

Peripheral nerve injury remains a clinical challenge with severe physiological and functional consequences. Despite the existence of multiple possible therapeutic approaches, until now, there is no consensus regarding the advantages of each option or the best methodology in promoting nerve regeneration. Regenerative medicine is a promise to overcome this medical limitation, and in this work, chitosan nerve guide conduits and olfactory mucosa mesenchymal stem/stromal cells were applied in different therapeutic combinations to promote regeneration in sciatic nerves after neurotmesis injury. Over 20 weeks, the intervened animals were subjected to a regular functional assessment (determination of motor performance, nociception, and sciatic indexes), and after this period, they were evaluated kinematically and the sciatic nerves and cranial tibial muscles were evaluated stereologically and histomorphometrically, respectively. The results obtained allowed confirming the beneficial effects of using these therapeutic approaches. The use of chitosan NGCs and cells resulted in better motor performance, better sciatic indexes, and lower gait dysfunction after 20 weeks. The use of only NGGs demonstrated better nociceptive recoveries. The stereological evaluation of the sciatic nerve revealed identical values in the different parameters for all therapeutic groups. In the muscle histomorphometric evaluation, the groups treated with NGCs and cells showed results close to those of the group that received traditional sutures, the one with the best final values. The therapeutic combinations studied show promising outcomes and should be the target of new future works to overcome some irregularities found in the results and establish the combination of nerve guidance conduits and olfactory mucosa mesenchymal stem/stromal cells as viable options in the treatment of peripheral nerves after injury.

Augmented peripheral nerve regeneration through elastic nerve guidance conduits prepared using a porous PLCL membrane with a 3D printed collagen hydrogel

Longitudinally oriented, 3D printed collagen hydrogel-grafted elastic nerve guidance conduits to promote nerve regeneration in peripheral nerve defects.

Biometric Data Comparison Between Lewis and Sprague Dawley Rats

Introduction: Pressure mapping systems are often used for indirect assessment of kinematic gait parameter differences after repair of critical peripheral nerve defects in small animal models. However, there does not appear to be any literature that studies the differences in normal gait pattern of Sprague Dawley rats compared to Lewis rats using a Tekscan VH4 pressure mat system. The purpose of this study is to assess the gait profile of Lewis and Sprague Dawley rats generated by Tekscan's VH4 system to detect similarities and/or differences in gait parameters involving both force and temporal variables. Materials and Methods: The gait profile of 14 Lewis and 14 Sprague Dawley rats was recorded using a Tekscan VH4 pressure map system with two successful walks per animal and gait parameter data was normalized for mean variance between the two rodent strains. Results: The results showed that temporal and normalized force parameters were not significantly different between the two types of rats. Maximum force, contact area, stride length, and adjusted pressure variables were significantly different between the two strains, likely attributed to the body size and weight differential between the strains. Variation in some of these parameters were considered due to differences in overall body size between the two strains, variations in gait kinematics between individual rodent subjects, and the limitations of the current experimental design. Conclusion: For future in vivo models, either Sprague Dawley or Lewis rat strains would be acceptable animal models when comparing base-line gait profiles using the Tekscan VH4 pressure map system when assessing critical defect repairs of peripheral nerves.

Paw-Print Analysis of Contrast-Enhanced Recordings (PrAnCER): A Low-Cost, Open-Access Automated Gait Analysis System for Assessing Motor Deficits

Gait analysis is used to quantify changes in motor function in many rodent models of disease. Despite the importance of assessing gait and motor function in many areas of research, the available commercial options have several limitations such as high cost and lack of accessible, open code. To address these issues, we developed PrAnCER, Paw-Print Analysis of Contrast-Enhanced Recordings, for automated quantification of gait. The contrast-enhanced recordings are produced by using a translucent floor that obscures objects not in contact with the surface, effectively isolating the rat's paw prints as it walks. Using these videos, our simple software program reliably measures a variety of spatiotemporal gait parameters. To demonstrate that PrAnCER can accurately detect changes in motor function, we employed a haloperidol model of Parkinson's disease (PD). We tested rats at two doses of haloperidol: high dose (0.30 mg/kg) and low dose (0.15 mg/kg). Haloperidol significantly increased stance duration and hind paw contact area in the low dose condition, as might be expected in a PD model. In the high dose condition, we found a similar increase in contact area but also an unexpected increase in stride length. With further research, we found that this increased stride length is consistent with the bracing-escape phenomenon commonly observed at higher doses of haloperidol. Thus, PrAnCER was able to detect both expected and unexpected changes in rodent gait patterns. Additionally, we confirmed that PrAnCER is consistent and accurate when compared with manual scoring of gait parameters.

Functional evaluation outcomes correlate with histomorphometric changes in the rat sciatic nerve crush injury model: A comparison between sciatic functional index and kinematic analysis

Elucidating whether there is a correlation between biomechanical functions and histomorphometric data in the rat sciatic nerve crush injury model would contribute to an accurate evaluation of the regeneration state without sacrificing animals. The gold standard for functional evaluation is the sciatic functional index (SFI) despite there being intrinsic shortcomings. Kinematic analysis is considered a reliable and sensitive approach for functional evaluation, most commonly assessed as ankle angle at various phases of a gait cycle. Studies utilizing the toe angle for functional evaluation are scarce, and changes in the toe angle following surgery remain unknown. The present study assessed correlations of ankle angle, toe angle and SFI with histomorphometric data, aiming to determine which parameters most accurately reflect changes in histomorphometric data over time. Six Lewis rats were designated as the control group. 30 animals received surgery, six of them were randomly selected on the first, second, third, fourth, and sixth week after surgery for measurements of ankle and toe angles in the “toe-off” phase, and for evaluation of SFI. Histomorphometric analysis were also performed, to determine the number of myelinated nerve fibers, diameters of myelinated nerve fibers, axon diameters, and myelin sheath thicknesses. Furthermore, we investigated changes in ankle angle, toe angle, SFI, and histomorphometric data over time, as well as correlations between ankle angle, toe angle, and SFI with histomorphometric data. The results revealed that changes in SFI, ankle angle, and toe angle highly correlate with histomorphometric data in the rat sciatic nerve crush injury model. Toe angle reflected changes in histomorphometric data with time more precisely than ankle angle or SFI did, and ankle angle was a better prognostic parameter than SFI.

Three-dimensional motion analysis for comprehensive understanding of gait characteristics after sciatic nerve lesion in rodents

Rodent models of sciatic nerve lesion are regularly used to assess functional deficits in nerves. Impaired locomotor functions induced by sciatic nerve lesion are currently evaluated with scoring systems despite their limitations. To overcome these shortcomings, which includes low sensitivity, little significance, and the representation of only marginal components of motion profiles, some additional metrics have been introduced. However, a quantitative determination of motion deficits is yet to be established. We used a three-dimensional motion analysis to investigate gait deficits after sciatic nerve lesion in rats. This enabled us to depict the distorted gait motion using both traditional parameters and novel readouts that are specific for the three-dimensional analysis. Our results suggest that three-dimensional motion analysis facilitates a comprehensive understanding of the gait impairment specifically, but not limited to, a sciatic lesion rat model. A broad application of these methods will improve understanding and standardized motor assessment.

A Machine Learning Approach to Automated Gait Analysis for the Noldus Catwalk System

OBJECTIVE

Gait analysis of animal disease models can provide valuable insights into in vivo compound effects and thus help in preclinical drug development. The purpose of this paper is to establish a computational gait analysis approach for the Noldus Catwalk system, in which footprints are automatically captured and stored.

METHODS

We present a - to our knowledge - first machine learning based approach for the Catwalk system, which comprises a step decomposition, definition and extraction of meaningful features, multivariate step sequence alignment, feature selection, and training of different classifiers (gradient boosting machine, random forest, and elastic net).

RESULTS

Using animal-wise leave-one-out cross validation we demonstrate that with our method we can reliable separate movement patterns of a putative Parkinson's disease animal model and several control groups. Furthermore, we show that we can predict the time point after and the type of different brain lesions and can even forecast the brain region, where the intervention was applied. We provide an in-depth analysis of the features involved into our classifiers via statistical techniques for model interpretation.

CONCLUSION

A machine learning method for automated analysis of data from the Noldus Catwalk system was established.

SIGNIFICANCE

Our works shows the ability of machine learning to discriminate pharmacologically relevant animal groups based on their walking behavior in a multivariate manner. Further interesting aspects of the approach include the ability to learn from past experiments, improve with more data arriving and to make predictions for single animals in future studies.

A novel endpoint for the assessment of chemotherapy-induced peripheral neuropathy in rodents: biomechanical properties of peripheral nerve

Chemotherapy-induced peripheral neuropathy (CiPN) is a frequent adverse effect in patients and a leading safety consideration in oncology drug development. Although behavioral assessment and microscopic examination of the nerves and dorsal root ganglia can be incorporated into toxicity studies to assess CiPN risk, more sensitive and less labor-intensive endpoints are often lacking. In this study, rats and mice administered vincristine (75 μg kg^-1  day^-1 , i.p., for 10 days in rats and 100 μg kg^-1  day^-1 , i.p., for 11 days in mice, respectively) were employed as the CiPN models. Behavioral changes were assessed during the dosing phase. At necropsy, the sural or sciatic nerve was harvested from the rats and mice, respectively, and assessed for mechanical and histopathological endpoints. It was found that the maximal load and the load/extension ratio were significantly decreased in the nerves collected from the animals dosed with vincristine compared with the vehicle-treated animals (P < 0.05). Additionally, the gait analysis revealed that the paw print areas were significantly increased in mice (P < 0.01), but not in rats following vincristine administration. Light microscopic histopathology of the nerves and dorsal root ganglia were unaffected by vincristine administration. We concluded that ex vivo mechanical properties of the nerves is a sensitive endpoint, providing a new method to predict CiPN in rodent. Gait analysis may also be a useful tool in these pre-clinical animal models.

Sporadic ALS Astrocytes Induce Neuronal Degeneration In Vivo

Astrocytes from familial amyotrophic lateral sclerosis (ALS) patients or transgenic mice are toxic specifically to motor neurons (MNs). It is not known if astrocytes from sporadic ALS (sALS) patients cause MN degeneration in vivo and whether the effect is specific to MNs. By transplanting spinal neural progenitors, derived from sALS and healthy induced pluripotent stem cells (iPSCs), into the cervical spinal cord of adult SCID mice for 9 months, we found that differentiated human astrocytes were present in large areas of the spinal cord, replaced endogenous astrocytes, and contacted neurons to a similar extent. Mice with sALS but not non-ALS cells showed reduced non-MNs numbers followed by MNs in the host spinal cord. The surviving MNs showed reduced inputs from inhibitory neurons and exhibited disorganized neurofilaments and aggregated ubiquitin. Correspondingly, mice with sALS but not non-ALS cells showed declined movement deficits. Thus, sALS iPSC-derived astrocytes cause ALS-like degeneration in both MNs and non-MNs.

Treatment with analgesics after mouse sciatic nerve injury does not alter expression of wound healing-associated genes

Animal models of sciatic nerve injury are commonly used to study neuropathic pain as well as axon regeneration. Administration of post-surgical analgesics is an important consideration for animal welfare, but the actions of the analgesic must not interfere with the scientific goals of the experiment. In this study, we show that treatment with either buprenorphine or acetaminophen following a bilateral sciatic nerve crush surgery does not alter the expression in dorsal root ganglion (DRG) sensory neurons of a panel of genes associated with wound healing. These findings indicate that the post-operative use of buprenorphine or acetaminophen at doses commonly suggested by Institutional Animal Care and Use Committees does not change the intrinsic gene expression response of DRG neurons to a sciatic nerve crush injury, for many wound healing-associated genes. Therefore, administration of post-operative analgesics may not confound the results of transcriptomic studies employing this injury model.

Functional evaluation of peripheral nerve regeneration and target reinnervation in animal models: a critical overview

Peripheral nerve injuries usually lead to severe loss of motor, sensory and autonomic functions in the patients. Due to the complex requirements for adequate axonal regeneration, functional recovery is often poorly achieved. Experimental models are useful to investigate the mechanisms related to axonal regeneration and tissue reinnervation, and to test new therapeutic strategies to improve functional recovery. Therefore, objective and reliable evaluation methods should be applied for the assessment of regeneration and function restitution after nerve injury in animal models. This review gives an overview of the most useful methods to assess nerve regeneration, target reinnervation and recovery of complex sensory and motor functions, their values and limitations. The selection of methods has to be adequate to the main objective of the research study, either enhancement of axonal regeneration, improving regeneration and reinnervation of target organs by different types of nerve fibres, or increasing recovery of complex sensory and motor functions. It is generally recommended to use more than one functional method for each purpose, and also to perform morphological studies of the injured nerve and the reinnervated targets.

Gait cycle analysis: parameters sensitive for functional evaluation of peripheral nerve recovery in rat hind limbs

BACKGROUND

Video-assisted gait kinetics analysis has been a sensitive method to assess rat sciatic nerve function after injury and repair. However, in conduit repair of sciatic nerve defects, previously reported kinematic measurements failed to be a sensitive indicator because of the inferior recovery and inevitable joint contracture.

OBJECTIVE

This study aimed to explore the role of physiotherapy in mitigating joint contracture and to seek motion analysis indices that can sensitively reflect motor function.

METHODS

Data were collected from 26 rats that underwent sciatic nerve transection and conduit repair. Regular postoperative physiotherapy was applied. Parameters regarding step length, phase duration, and ankle angle were acquired and analyzed from video recording of gait kinetics preoperatively and at regular postoperative intervals.

RESULTS

Stride length ratio (step length of uninjured foot/step length of injured foot), percent swing of the normal paw (percentage of the total stride duration when the uninjured paw is in the air), propulsion angle (toe-off angle subtracted by midstance angle), and clearance angle (ankle angle change from toe off to midswing) decreased postoperatively comparing with baseline values. The gradual recovery of these measurements had a strong correlation with the post-nerve repair time course.

CONCLUSIONS

Ankle joint contracture persisted despite rigorous physiotherapy. Parameters acquired from a 2-dimensional motion analysis system, that is, stride length ratio, percent swing of the normal paw, propulsion angle, and clearance angle, could sensitively reflect nerve function impairment and recovery in the rat sciatic nerve conduit repair model despite the existence of joint contractures.

Effect of low-level laser therapy (685 nm, 3 J/cm(2)) on functional recovery of the sciatic nerve in rats following crushing lesion

Previous studies have shown that low-level laser therapy (LLLT) promotes posttraumatic nerve regeneration. The objective of the present study was to assess the efficacy of 685-nm LLLT at the dosage of 3 J/cm(2) in the functional recovery of the sciatic nerve in rats following crushing injury. The left sciatic nerves of 20 male Wistar rats were subjected to controlled crush injury by a hemostatic tweezers, and the rats were randomly allocated into two experimental groups as follows: control group and laser group. Laser irradiation (685 nm wavelength; 15 mW, CW, 3 J/cm(2), spot of 0.028 cm(2)) was started on the postsurgical first day, above the site of injury, and was continued for 21 consecutive days. Functional recovery was evaluated at 3 weeks postoperatively by measuring the sciatic functional index (SFI) and sciatic static index (SSI) at weekly intervals. The treated rats showed improvement in motion pattern. The SFI and SSI results were significant when comparing two groups on the 14th and 21st postoperative days (p < 0.05). There were intra-group differences detected in laser group in different periods (p < 0.05). Low-level laser irradiation, with the parameters used in the present study, accelerated and improved sciatic nerve function in rats after crushing injury.

Functional recovery after repair of peroneal nerve gap using different collagen conduits

BACKGROUND

Currently, autologous nerve implantation to bridge a long nerve gap presents the greatest regenerative performance in spite of substantial drawbacks. In this study, we evaluate the effect of two different collagen conduits bridging a peroneal nerve gap.

METHODS

Rats were divided into four groups: (1) the gold standard group, in which a 10-mm-long nerve segment was cut, reversed, and reimplanted between the nerve stumps; (2) the CG-I/III group, in which a type I/III collagen conduit bridged the gap; (3) the CG-I, in which a type I collagen conduit was grafted; and (4) the sham group, in which a surgery was performed without injuring the nerve. Peroneal Functional Index and kinematics analysis of locomotion were performed weekly during the 12 weeks post-surgery. At the end of the protocol, additional electrophysiological tests, muscular weight measurements, axon counting, and g-ratio analysis were carried out.

RESULTS

Functional loss followed by incomplete recovery was observed in animals grafted with collagen conduits. At 12 weeks post-surgery, the ventilatory rate of the CG-I group in response to exercise was similar to the sham group, contrary to the CG-I/III group. After KCl injections, an increase in metabosensitive afferent-fiber activity was recorded, but the response stayed incomplete for the collagen groups compared to the sham group. Furthermore, the CG-I group presented a higher number of axons and seemed to induce a greater axonal maturity compared to the CG-I/III group.

CONCLUSIONS

Our results suggest that the grafting of a type I collagen conduit may present slight better prospects than a type I/III collagen conduit.

Gait compensations in rats after a temporary nerve palsy quantified using temporo-spatial and kinematic parameters

BACKGROUND

The aim of this work was to test a method for measuring the gait of rats with sufficient sensitivity to detect subtle locomotor changes due to pathology, injury and recovery.

METHOD

The gait of female Sprague-Dawley rats was assessed using an optical motion tracking system and the DigiGait™ imaging system during normal locomotion, shortly after temporary nerve block to the left hind limb and after full recovery.

RESULTS

The effect of low treadmill speeds (10-30 cm/s) was initially investigated. Significant changes were detected in the spatiotemporal gait parameters, consistent with those previously reported. The overall ranges of motion in the hip, knee and ankle joints were 37.5° (±7.1°), 50.2° (±9.4°) and 61.6° (±9.1°) and did not appear to change with speed, indicating that for low speed variations, kinematic comparisons across speeds may be possible. Following the induction of a temporary sciatic nerve block, the range of motion of the left ankle and knee during swing decreased by 23° and 33°, respectively (p<0.05). A compensatory change of a greater range of motion at the hip was noted in the contralateral limb (p<0.01). 90 min post injection, most of the gait parameters had returned to normal, however, minor walking deficits were still present.

COMPARISON WITH EXISTING METHOD(S)

Discriminant analysis showed that a combination of dynamic and kinematic parameters provides a more robust method for the classification of gait changes.

CONCLUSIONS

This more detailed method, employing both dynamic analysis and joint kinematics simultaneously, was found to be a reliable approach for the quantification of gait in rats.

Detection of subtle neurological alterations by the Catwalk XT gait analysis system

BACKGROUND

A new version of the CatWalk XT system was evaluated as a tool for detecting very subtle alteration in gait based on higher speed sample rate; the system could also demonstrate minor changes in neurological function. In this study, we evaluated the neurological outcome of sciatic nerve injury intervened by local injection of hyaluronic acid. Using the CatWalk XT system, we looked for differences between treated and untreated groups and differences within the same group as a function of time so as to assess the power of the Catwalk XT system for detecting subtle neurological change.

METHODS

Peripheral nerve injury was induced in 36 Sprague-Dawley rats by crushing the left sciatic nerve using a vessel clamp. The animals were randomized into one of two groups: Group I: crush injury as the control; Group II: crush injury and local application with hyaluronic acid. These animals were subjected to neurobehavior assessment, histomorphology evaluation, and electrophysiology study periodically. These data were retrieved for statistical analysis.

RESULTS

The density of neurofilament and S-100 over the distal end of crushed nerve showed significant differences either in inter-group comparison at various time points or intra-group comparison from 7 to 28 days. Neuronal structure architecture, axon counts, intensity of myelination, electrophysiology, and collagen deposition demonstrate significant differences between the two groups. There was significant difference of SFI and angle of ankle in inter- group analysis from 7 to 28 days, but there were no significant differences in SFI and angle of ankle at time points of 7 and 14 days. In the Cat Walk XT analysis, the intensity, print area, stance duration, and swing duration all showed detectable differences at 7, 14, 21, and 28 days, whereas there were no significant difference at 7 and 14 days with CatWalk 7 testing. In addition, there were no significant differences of step sequence or regularity index between the two versions.

CONCLUSION

Hyaluronic acid augmented nerve regeneration as early as 7 days after crush injury. This subtle neurological alteration could be detected through the CatWalk XT gait analysis but not the SFI, angle of ankle, or CatWalk 7 methods.

Misdirection and guidance of regenerating axons after experimental nerve injury and repair

Misdirection of regenerating axons is one of the factors that can explain the limited results often found after nerve injury and repair. In the repair of mixed nerves innervating different distal targets (skin and muscle), misdirection may, for example, lead to motor axons projecting toward skin, and vice versa—that is, sensory axons projecting toward muscle. In the repair of motor nerves innervating different distal targets, misdirection may result in reinnervation of the wrong target muscle, which might function antagonistically. In sensory nerve repair, misdirection might give an increased perceptual territory. After median nerve repair, for example, this might lead to a dysfunctional hand.

Different factors may be involved in the misdirection of regenerating axons, and there may be various mechanisms that can later correct for misdirection. In this review the authors discuss these different factors and mechanisms that act along the pathway of the regenerating axon. The authors review recently developed evaluation methods that can be used to investigate the accuracy of regeneration after nerve injury and repair (including the use of transgenic fluorescent mice, retrograde tracing techniques, and motion analysis). In addition, the authors discuss new strategies that can improve in vivo guidance of regenerating axons (including physical guidance with multichannel nerve tubes and biological guidance accomplished using gene therapy).

Functional evaluation in the rat sciatic nerve defect model: a comparison of the sciatic functional index, ankle angles, and isometric tetanic force

BACKGROUND

The sciatic functional index has long been the standard method of assessing motor recovery in the rat sciatic nerve model. The relative subjective nature of the assessment has led to development of newer methods, including video gait analysis and quantitative measurement of isometric tetanic muscle force.

METHODS

Forty male Lewis rats, each with a 10-mm segmental defect in the sciatic nerve, were divided randomly into two groups: rats in group I underwent repair with reversed autograft, and those in group II received a collagen conduit. Video gait analyses were performed at 0, 4, 8, and 12 weeks, and sciatic functional index and ankle angles in four different walking phases were recorded. Isometric tetanic force of the tibialis anterior muscle was also measured at 12 weeks and correlated with sciatic functional index and video gait analysis data.

RESULTS

The sciatic functional index results did not correlate with isometric tetanic force. Significantly, the sciatic functional index could not be measured in 26 percent of the rats at 8 weeks and 59 percent of the rats at 12 weeks secondary to toe contractures. Among various ankle angle measurements, only the ankle angle in toe-off phase correlated well with isometric tetanic force.

CONCLUSIONS

Toe contractures occurred more frequently in rats with better nerve recovery, and interfered with evaluation of the motor recovery using the sciatic functional index method. Ankle angle in toe-off phase measured from video gait analysis is a useful parameter that reflects functional recovery of the muscle force.

The lateral thoracic nerve and the cutaneous maximus muscle--a novel in vivo model system for nerve degeneration and regeneration studies

We report a novel in vivo mouse model system to study regeneration of injured motor nerve and spatiotemporal pattern of denervation in experimental nerve diseases. The lateral thoracic nerve (LTN), as a pure motor nerve, innervates the cutaneous maximus muscle (CMM) by some of the shortest and the longest motor nerve fibers in the mouse body. Its branches and nerve terminals can be imaged in whole mount preparations. Here we describe the branching pattern of the LTN and its innervation of the CMM, and characterize degeneration and regeneration over time after a LTN crush by morphological and electrophysiological analyses. We demonstrate the utility of this model in a well-established neurotoxicity paradigm and in a genetic disease model of the peripheral neuropathy. Furthermore, this system enables punch biopsies that allow repeated and multi-location examinations for LTN regeneration and CMM reinnervation over time. The presence of the LTN and the CMM in a variety of species and its easy accessibility suggests that this in vivo model system offers considerable promise for future nerve degeneration and regeneration research.

Peripheral nerve reconstruction with collagen tubes filled with denatured autologous muscle tissue in the rat model

Conventional nerve conduits lack cellular and extracellular guidance structures critical for bridging larger defects. In this study, an exogenous matrix for axonal regeneration was provided by pretreated muscle tissue. In 24 rats, 14-mm sciatic nerve segments were resected and surgically reconstructed using one of the following methods: autograft (AG); bovine type I collagen conduit; (MDM) collagen tube filled with modified denatured autologous muscle tissue. For 8 weeks, functional regeneration was evaluated by footprint and video gait analysis. Evaluation was complemented by electrophysiology, as well as qualitative and quantitative structural assessment of nerves and target muscles. Group AG was superior both structurally and functionally, showing higher axon counts, a more normal gait pattern, and less severe muscle atrophy. Fiber quality (fiber size and myelin thickness) was highest in group MDM, possibly related to the myelin-producing effect of muscular laminin. However, axon count was lowest in this group, and ultrastructural analysis of the denatured muscle tissue showed areas of incomplete denaturation that had acted as a mechanical barrier for regenerating axons. In light of these results, the often advocated use of muscular exogenous matrix for peripheral nerve reconstruction is reviewed in the literature, and its clinical application is critically discussed. In conclusion, combined muscle tubes may have a positive influence on nerve fiber maturation. However, muscle pretreatment is not without risks, and denaturation processes need to be further refined.

Potentials and limitations of peripheral nerve injury models in rodents with particular reference to the femoral nerve

Restoration of function after peripheral nerve repair in humans is unsatisfactory. Various causes of poor recovery have been proposed. Still, we do not understand which of these potential factors are indeed detrimental and do not know how to manipulate them experimentally in a clinically feasible way. Future success largely depends on methodological improvement in rodent models. An example of recent progress is the introduction of new functional and anatomical outcome measures in the facial nerve injury paradigm which led to novel insights into facial nerve regeneration and a new therapeutic concept. Less success can be ascribed to the use of the classical spinal nerve model, the sciatic nerve paradigm, not least because of its anatomical and functional complexity making assessment of recovery challenging. A simpler alternative to the sciatic nerve is the femoral nerve model. It offers, alongside with its known usefulness for studies on precision of motor reinnervation, the possibility of reliable functional assessments and a straightforward search of anatomical substrates of dysfunction. The structure-function approach in the femoral nerve paradigm has been useful for testing of novel therapeutic means and analyses of regeneration in mutant mice. The potential of the method has still not been really exploited and its more extensive use may contribute to better understanding of nerve regeneration.

Sciatic nerve regeneration by microporous nerve conduits seeded with glial cell line-derived neurotrophic factor or brain-derived neurotrophic factor gene transfected neural stem cells

Neurotrophic factors such as the glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) promote nerve cell survival and regeneration, but their efficacy in repairing a longer gap defect of rat sciatic nerve (15 mm) has not been established. In this study, two recombinant mammalian vectors containing either rat GDNF gene or BDNF gene were constructed and each was transfected into neural stem cells (NSCs). It was found that the transfection of GDNF or BDNF gene into NSCs led to significantly enhanced expression of GDNF or BDNF mRNA. The amount of GDNF or BDNF protein secreted from the transfected NSCs showed a 3.3-fold or 2.5-fold increase than that from nontransfected NSCs, respectively. The regeneration capacity of rat sciatic nerve in a poly(D,L-lactide) conduit seeded with GDNF or BDNF-transfected NSCs was evaluated by the histology, functional gait, and electrophysiology after 8 weeks of implantation. It was observed that the degree of myelination and the size of regenerated tissue in the conduits seeded with GDNF- and BDNF-transfected NSCs were higher than those seeded with the nontransfected NSCs. Conduits seeded with GDNF-transfected NSCs had the greatest number of blood vessels. The functional recovery assessed by the functional gait and electrophysiology was significantly improved for conduits seeded with GDNF or BDNF-transfected NSCs. It was concluded that the genetically modified NSCs may have potential applications in promoting nerve regeneration and functional recovery.

A novel motion analysis approach reveals late recovery in C57BL/6 mice and deficits in NCAM-deficient mice after sciatic nerve crush

Assessment of motor abilities after sciatic nerve injury in rodents, in particular mice, relies exclusively on walking track (footprint) analysis despite known limitations of this method. Using principles employed recently for video-based motion analyses after femoral nerve and spinal cord injuries, we have designed and report here a novel approach for functional assessments after sciatic nerve lesions in mice. Functional deficits are estimated by angle and distance measurements on single video frames recorded during beam-walking and inclined ladder climbing. Analyses of adult C57BL/6J mice after crush of the sciatic, tibial, or peroneal nerve allowed the identification of six numerical parameters, detecting impairments of the plantar flexion of the foot and the toe spread. Some of these parameters, as well as footprint functional indices, revealed severe impairment after crush injury of the sciatic or tibial, but not the peroneal nerve, and complete recovery within 3 weeks after lesion. Other novel estimates, however, showed that complete recovery is reached as late as 2-3 months after sciatic nerve crush. These measures detected both tibial and peroneal dysfunction. In contrast to the complete restoration of function in wild-type mice (100%), our new parameters, in contrast to the sciatic functional index, showed incomplete recovery (85%) 90 days after sciatic nerve crush in mice deficient in the neural cell adhesion molecule (NCAM). We conclude that the novel video-based approach is more precise, sensitive, and versatile than established tests, allowing objective numerical assessment of different motor functions in a sciatic nerve injury paradigm in mice.

Characteristics of locomotion, muscle strength, and muscle tissue in regenerating rat skeletal muscles

Although numerous studies have aimed to elucidate the mechanisms used to repair the structure and function of injured skeletal muscles, it remains unclear how and when movement recovers following damage. We performed a temporal analysis to characterize the changes in movement, muscle function, and muscle structure after muscle injury induced by the drop-mass technique. At each time-point, movement recovery was determined by ankle kinematic analysis of locomotion, and functional recovery was represented by isometric force. As a histological analysis, the cross-sectional area of myotubes was measured to examine structural regeneration. The dorsiflexion angle of the ankle, as assessed by kinematic analysis of locomotion, increased after injury and then returned to control levels by day 14 post-injury. The isometric force returned to normal levels by day 21 post-injury. However, the size of the myotubes did not reach normal levels, even at day 21 post-injury. These results indicate that recovery of locomotion occurs prior to recovery of isometric force and that functional recovery occurs earlier than structural regeneration. Thus, it is suggested that recovery of the movement and function of injured skeletal muscles might be insufficient as markers for estimating the degree of neuromuscular system reconstitution.

High-speed X-ray video demonstrates significant skin movement errors with standard optical kinematics during rat locomotion

The sophistication of current rodent injury and disease models outpaces that of the most commonly used behavioral assays. The first objective of this study was to measure rat locomotion using high-speed X-ray video to establish an accurate baseline for rat hindlimb kinematics. The second objective was to quantify the kinematics errors due to skin movement artefacts by simultaneously recording and comparing hindlimb kinematics derived from skin markers and from direct visualization of skeletal landmarks. Joint angle calculations from skin-derived kinematics yielded errors as high as 39 degrees in the knee and 31 degrees in the hip around paw contact with respect to the X-ray data. Triangulation of knee position from the ankle and hip skin markers provided closer, albeit still inaccurate, approximations of bone-derived, X-ray kinematics. We found that soft tissue movement errors are the result of multiple factors, the most impressive of which is overall limb posture. Treadmill speed had surprisingly little effect on kinematics errors. These findings illustrate the significance and context of skin movement error in rodent kinematics.

Measuring nerve regeneration in the mouse

Genetic engineering of mice has become a major tool in understanding the roles of individual molecules in regeneration of nerves, and will play an increasing role in the future. Mice are in many ways well suited to assessment both of nerve regeneration after axotomy and of collateral sprouting of intact fibers into areas of denervation. However, mouse models present special challenges because of their small size, their inherent capacity for regeneration, and the potential strain effects. The most widely used model of regeneration, sciatic nerve injury, has its inherent limitations, and there is a need for other models of injury to long nerves. Measures of regeneration in the mouse can be divided into those that assess the latency to initiate growth, those sensitive to the rate of growth and the proportion of fibers growing at fast rates, those that assess the time to reinnervation of specific targets and the completeness of reinnervation, and those that assess specificity of reinnervation and functional recovery. The short length of nerve available in the mouse limits measures of the rates of outgrowth, and thus introduces a greater potential for "noise" of measurement than is seen in larger animals such as the rat. For both regeneration of interrupted fibers and collateral regeneration from intact fibers histological and physiological measures of "time to target" have the advantages of direct correlation with restoration of function, the ability to assess regeneration of different fiber types efficiently, and the fact that most of these measures are easier in the mouse than in the rat.

Functional recovery after implantation of artificial nerve grafts in the rat- a systematic review

Purpose

The aim of this study was to compare functional data of different nerve-gap bridging materials evaluated in rat experiments by means of a systematic review.

Materials and methods

A systematic review was conducted, searching MEDLINE, HTS and CENTRAL to identify all trials evaluating functional recovery of artificial nerve conduits in the rat model.

Results

There was a trend towards a favourable outcome of conduits coated with Schwann-cells compared to the plain synthetics. Histomorphometry, electrophysiology and muscle-weight correlated poorly with functional outcome.

Conclusion

Schwann-cell coated conduits showed promising results concerning functional recovery. Further standardization in outcome reporting is encouraged.

Quantification of gait in dystonic Gunn rats

Spontaneously jaundiced Gunn rats exposed to sulfadimethoxine develop bilirubin encephalopathy (kernicterus) with hearing loss and dystonia, closely resembling the human syndrome. We recently characterized the electromyographic activity in this animal model supporting our clinical impression of dystonia. The objective of this study was to develop a simple, non-invasive method to quantify the motor deficits in dystonic rodents. On postnatal day 16, Gunn rats were treated with 100mg/kg of sulfadimethoxine or saline. On postnatal day 31, the ventral view of the animals was videotaped while the animals walked inside a Plexiglas chamber. Individual video frames were reviewed and specific gait parameters including hindlimb spread, step length ratio variability, stance/swing ratio and walking speed were compared between dystonic and non-dystonic jaundiced and non-jaundiced littermates. Data analysis demonstrated statistically significant increases in hindlimb spread and step length ratio variability and decreases in walking speed in dystonic animals as compared to controls. This study demonstrates a valuable technique to objectively characterize dystonia in Gunn rats, which could have wide use for other experimental movement disorders as well.

Functional recovery after peripheral nerve injury and implantation of a collagen guide

Although surgery techniques improved over the years, the clinical results of peripheral nerve repair remain unsatisfactory. In the present study, we compare the results of a collagen nerve guide conduit to the standard clinical procedure of nerve autografting to promote repair of transected peripheral nerves. We assessed behavioral and functional sensori-motor recovery in a rat model of peroneal nerve transection. A 1cm segment of the peroneal nerve innervating the Tibialis anterior muscle was removed and immediately replaced by a new biodegradable nerve guide fabricated from highly purified type I+III collagens derived from porcine skin. Four groups of animals were included: control animals (C, n=12), transected animals grafted with either an autologous nerve graft (Gold Standard; GS, n=12) or a collagen tube filled with an acellular skeletal muscle matrix (Tube-Muscle; TM, n=12) or an empty collagen tube (Collagen-Tube; CT, n=12). We observed that 1) the locomotor recovery pattern, analyzed with kinetic parameters and peroneal functional index, was superior in the GS and CT groups; 2) a muscle contraction was obtained in all groups after stimulation of the proximal nerve but the mechanical muscle properties (twitch and tetanus threshold) parameters indicated a fast to slow fiber transition in all operated groups; 3) the muscular atrophy was greater in animals from TM group; 4) the metabosensitive afferent responses to electrically induced fatigue and to two chemical agents (KCl and lactic acid) was altered in GS, CT and TM groups; 5) the empty collagen tube supported motor axonal regeneration. Altogether, these data indicate that motor axonal regeneration and locomotor recovery can be obtained with the insertion of the collagen tube RevolNerv. Future studies may include engineered conduits that mimic as closely as possible the internal organization of uninjured nerve.

Variations in glial cell line-derived neurotrophic factor release from biodegradable nerve conduits modify the rate of functional motor recovery after rat primary nerve repairs

Accelerating axonal regeneration to shorten the delay of reinnervation and improve functional recovery after a peripheral nerve lesion is a clinical demand and an experimental challenge. We developed a resorbable nerve conduit (NC) for controlled release of glial cell line-derived neurotrophic factor (GDNF) with the aim of assessing motor functional recovery according to the release kinetics of this factor in a short gap model. Different types of resorbable NCs were manufactured from a collagen tube and multiple coating layers of poly(lactide-coglycolide), varying in poly(lactide-coglycolide) type and coating thickness to afford three distinct release kinetics of the neurotrophic factor. GDNF release was quantified in vitro. End-to-end suture and GDNF-free NC served as controls. Thirty-five Wistar rats underwent surgery. Motor recovery was followed from 1 to 12 weeks after surgery by video gait analysis. Morphometrical data were obtained at mid-tube level and distal to the NC. NCs were completely resorbed within 3 months with minimal inflammation. GDNF induced a threefold overgrowth of fibers at mid-tube level. However, the number of fibers was similar in the distal segment of all groups. The speed of recovery was inversely proportional to the number of fibers at the NC level but the level of recovery was similar for all groups at 3 months. The resorbable conduits proved their ability to modulate axonal regrowth through controlled release of GDNF. In relation to the dose delivered, GDNF strikingly multiplied the number of myelinated fibers within the NC but this increase was not positively correlated with the return of motor function in this model.